Critical investigation of the mechanisms at work in EMDR

Eye movement desensitization and reprocessing (EMDR) is a treatment-of-choice
for posttraumatic stress disorder (PTSD) in many western countries. However,
EMDR is not effective for about one-third of patients, and little is known
about its underlying mechanisms. A unique component of EMDR therapy is that
patients recall the traumatic memory and engage in horizontal eye movement (EM)
simultaneously, which has been shown to add to its efficacy. How can this be
explained? In recent years, growing attention has been paid to working memory
theory. It holds that EM during recall of a (traumatic) memory causes a
competition for limited working memory resources. By consequence, visual
imagery becomes less vivid and less emotional. While this theory held up to
rigorous testing, it is silent about how the immediate changes in memory
phenomenology result in PTSD symptom reduction. Without such explanation, the
clinical relevance of the existing knowledge is questionable. Two theoretical
possibilities have been proposed. First, the direct loss in memory detail may
be reconsolidated in long-term memory, causing future recollections to evoke
less extreme emotional responses. Alternatively, it has been suggested that the
empowering experience of holding a diluted traumatic memory in mind changes
dysfunctional beliefs about the trauma memory (e.g., *I can now focus on it
without becoming upset*), much like how exposure therapy works. The current
research will test the latter hypothesis.

The aim is to test whether EM in EMDR contributes to a reduction in
dysfunctional beliefs about recalling the traumatic memory. A sample of Dutch
veterans diagnosed with PTSD will be tested. During three EMDR treatment
sessions we will measure changes in memory vividness and emotionality (typical
for experimental research on EMDR) and appraisals of memory recall (unique to
the current research).

This study will cover the first three EMDR treatment sessions. A first session
will provide baseline measurements. The second and third sessions will comprise
recall of the trauma memory, one session with EM, the other one without. During
each session participants will fillout a series of short questionnaires. By
means of a cross-over experimental design for every partipant one session
(either session two or three, depending on randomised allocation) will be
devoid of the eye movement component. As such, participants serve as their own
control group.

See "Study design": not applying the eye movements in one of the EMDR treatment
sessions can be considered an intervention.

Burdens are that participants have to fill out questionnaires. Filling out the
questionnaires may elicit feelings of discomfort as they refer to the trauma
memory. There are no risks associated with participation.